Method, mobile station, system and network processor for use in mobile communications

A mobile communication system comprising:

• a mobile station;
• a first network wirelessly serving the mobile station as a home network when the mobile station is within the vicinity of the home network;
• a second network serving the mobile station as a visited network when the mobile station is within the vicinity of the visited network, and
• wherein the mobile station is configured to receive from the home network a certified service record of communication services, the certified service record including a service record and a certificate code, the service record indicating, as determined by the home network, types of communications services permitted to be provided to the mobile station by a visited network when the mobile station roams to a visited network, and the certificate code being a code generated by a calculation procedure applied to a contents of the service record, the mobile station storing the certified service record in its memory;
• and the authentication key is being retrieved from a key issuing terminal;
• wherein the mobile station is further configured to, in response to the mobile station roaming from the home network to the visited network, retrieve the certified service record from its memory and communicate the certified service record to the visited network so that the visited network may know the types of communication services it is permitted to provide to the mobile station;
• wherein the visited network is configured to provide communication services to the mobile station as a function of the types of communication services indicated in the service record in response to the visited network receiving the certified service record and authenticating the service record by calculating an authentication code using the received service record and an authentication key, obtained from key issuing terminal and held by the visited network, and matching the calculated authentication code with the certificate code sent by the mobile station.